<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>验证</title>
    <style type="text/css">
        * {
            padding: 0;
            margin: 0;
        }

        .box {
            background-color: #007AFF;
            margin-bottom: -100px;
            height: 200px;
        }

        .t {
            background-color: #f00;
            height: 20px;
            width: 200px;
        }
    </style>
</head>
<body>
<div class="box">高度为200px</div>
<div class="t">高度为20px</div>
</body>
</html>